Regardless of whether L is even or odd, the first element of the vector returned by fft is always the DC component. No matter what.
So, using the full frequency span, the frequency vector is computed as
L = length(X);
dF = Fs/L;
f = dF*(0:L-1)';
This code is correct for any length L, whether even or odd.
For the one-sided span, the code becomes:
f = dF*(0:floor(L/2)-1)';
For the two-sided span centered on DC, the code becomes:
f = (-Fs/2:dF:Fs/2-dF)' + mod(L,2)*dF/2;
Again, this code is correct for both even and odd L.